Optical method and system for light field displays having light-steering layers and periodic optical layer

ABSTRACT

A light-emitting layer of an apparatus includes an addressable array of light-emitting elements including a first light-emitting element and a periodic optical layer overlaying the light-emitting layer. The periodic optical layer includes at least a first periodic optical feature having a first optical power and a second periodic optical feature having a different optical power. A first controllable light-steering layer is disposed between the light-emitting layer and the periodic optical layer. The first controllable light-steering layer is switchable between directing light from the first light-emitting element through the first periodic optical feature and directing light from the first light-emitting element through the second periodic optical feature.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage application under 35 U.S.C.§ 371 of International Application No. PCT/US20/27274, titled “OPTICALMETHOD AND SYSTEM FOR LIGHT FIELD DISPLAYS HAVING LIGHT-STEERING LAYERSAND PERIODIC OPTICAL LAYER” filed on Apr. 8, 2020, which is anon-provisional filing of, and claims benefit under 35 U.S.C. § 119(e)from, U.S. Provisional Patent Application Ser. No. 62/833,427 titled“OPTICAL METHOD AND SYSTEM FOR LIGHT FIELD DISPLAYS BASED ON LIGHTSTEERING ELEMENTS AND PERIODIC OPTICAL LAYER” and filed Apr. 12, 2019,which application is hereby incorporated by reference in its entirety.

BACKGROUND

Different 3D displays, also referred to as display devices, can beclassified on the basis of their form factors into different categories.Head-mounted devices (HMD) occupy less space than goggleless solutions,which also means that HMDs can be made with smaller components and lessmaterials making them relatively low cost. Because head mounted VirtualReality (VR) goggles and smart glasses are single-user devices, they donot allow shared experiences as naturally as goggleless solutions.Volumetric 3D displays take up space in all three spatial directions andgenerally call for a lot of physical material, making these systemsheavy, expensive to manufacture, and difficult to transport. Due to thelarge size, the volumetric displays also tend to have small windows andlimited field-of view (FOV). Screen-based 3D displays typically have onelarge but flat component, which is the screen, and a system thatprojects the image(s) over free space from a distance. Screen-based 3Ddisplay systems can be more compact for transportation and also covermuch larger FOVs than, for example, volumetric displays. These systemscan be complex and expensive because they require projectorsub-assemblies and accurate alignment between the different parts,making them best for professional use. Flat form-factor 3D displays mayrequire a lot of space in two spatial directions, but because the thirddirection is only virtual, flat form-factor 3D displays are relativelyeasy to transport to and assemble in different environments. Becausethese devices are flat, at least some of their optical components aremore likely to be manufactured in sheet or roll format, making thesedevices relatively low cost in large volumes.

The human mind perceives and determines depths of observed objects inpart by receiving signals from muscles used to orient each eye. Thebrain associates the relative angular orientations of the eyes with thedetermined depths of focus. Correct focus cues give rise to a naturalblur on objects outside of an observed focal plane and a natural dynamicparallax effect. One type of 3D display capable of providing correctfocus cues uses volumetric display techniques that can produce 3D imagesin true 3D space. Each voxel of a 3D image is located physically at thespatial position where the voxel is supposed to be displayed andreflects or emits light from that position toward the observers to forma real image in the eyes of viewers. The main problems with 3Dvolumetric displays are their low resolution, large physical size, andexpensive manufacturing costs. These issues make 3D volumetric displaystoo cumbersome to use outside of special situations, e.g., productdisplays, museums, shows, and so forth. Another type of 3D displaycapable of providing correct retinal focus cues is a holographicdisplay. Holographic displays reconstruct whole light wavefrontsscattered from objects in natural settings. The main problem with thistechnology is a lack of suitable Spatial Light Modulator (SLM) componentthat could be used in the creation of the extremely detailed wavefronts.

A further type of 3D display technology capable of providing naturalretinal focus cues is called the Light Field (LF) display. LF displaysystems are designed to create light fields that represent light raystravelling in space in all directions. LF systems aim to control lightemissions both in spatial and angular domains, unlike the conventionalstereoscopic 3D displays that basically only control the spatial domainwith higher pixel densities. At least two fundamentally different waysto create light fields are utilized by many light field displays. In oneapproach, parallax is created across each individual eye of the viewerto produce the correct retinal blur corresponding to the 3D location ofthe object being viewed. This parallax can be performed by presentingmultiple views per single eye. The second approach is amulti-focal-plane approach, in which an object's image is projected toan appropriate focal plane corresponding to its 3D location.

In current relatively low-density multi-view imaging displays, the viewschange in a coarse stepwise fashion as the viewer moves in front of thedevice. This movement lowers the quality of 3D experience and can causea complete breakdown of 3D perception. In order to mitigate this problemand VAC, some Super Multi View (SMV) techniques have been implementedwith as many as 512 views. The idea is to generate an extremely largenumber of views to make any transition between two viewpoints verysmooth. If the light from at least two images from slightly differentviewpoints enters the eye pupil simultaneously, a much more realisticvisual experience follows. In this situation, motion parallax effectsresemble the natural conditions better as the brain unconsciouslypredicts the image change due to motion. The SMV condition can be met byreducing the interval between two views at the correct viewing distanceto a smaller value than the size of the eye pupil. The maximum angulardensity that can be achieved with SMV displays is limited bydiffraction, and an inverse relationship between spatial resolution(pixel size) and angular resolution exists. Diffraction increases theangular spread of a light beam passing through an aperture and thiseffect may be considered in the design of very high density SMVdisplays.

SUMMARY

A light-emitting layer of an apparatus includes an addressable array oflight-emitting elements including a first light-emitting element and aperiodic optical layer overlaying the light-emitting layer. The periodicoptical layer includes at least a first periodic optical feature havinga first optical power and a second periodic optical feature having adifferent optical power. A first controllable light-steering layer isdisposed between the light-emitting layer and the periodic opticallayer. The first controllable light-steering layer is switchable betweendirecting light from the first light-emitting element through the firstperiodic optical feature and directing light from the firstlight-emitting element through the second periodic optical feature.

The first periodic optical feature and the second periodic opticalfeature may be included in a first optical region. The periodic opticallayer may comprise a repeating pattern of optical regions arrangedsimilarly to the first optical region. A converging lens layer may bedisposed between the light-emitting layer and the periodic opticallayer. The converging lens layer may comprise a two-dimensional array ofconverging lenses, and wherein each converging lens is associated withat least one of the light-emitting elements in a projector cell. Eachprojector cell may include a corresponding optical region of theperiodic optical layer. Different sections of the first light-steeringlayer may be associated with different projector cells and may beseparately controllable. The first periodic optical feature may beoperative to focus light from at least the first light-emitting elementat a first distance from the periodic optical layer, and the secondperiodic optical feature may be operative to focus light from at leastthe first light-emitting element at a second distance from the periodicoptical layer, wherein the second distance is different from the firstdistance. The first controllable light-steering layer may comprise atleast one liquid crystal light-steering layer. The light-emitting layermay further comprise a second light-emitting element. The periodicoptical layer may further comprise a third periodic optical featurehaving a first tilt direction and a fourth periodic optical featurehaving a second tilt direction different from the first tilt direction.The first controllable light-steering layer may be switchable betweendirecting light from the second light-emitting element through the thirdperiodic optical feature and directing light from the secondlight-emitting element through the fourth periodic optical feature. Theapparatus may further comprise a second controllable light-steeringlayer between the light-emitting layer and the periodic optical layer.The first light-steering layer may be configured to deflect light in afirst plane, and the second light-steering layer may be configured todeflect light in a second plane substantially perpendicular to the firstplane. The first light-steering layer and the second light-steeringlayer may each be configured to deflect light in a first plane.

A method comprises displaying an image comprising a plurality of voxelsincluding a first voxel at a first voxel position by selectivelyemitting first light by a first light-emitting element of alight-emitting layer comprising a plurality of light-emitting elementsand operating a first section of a controllable light-steering layer toselectively direct light toward a first periodic optical feature of aperiodic optical layer comprising a plurality of periodic opticalfeatures, wherein the first periodic optical feature focuses the firstlight onto the first voxel position.

The method may further comprise selectively emitting second light by asecond light-emitting element of the light-emitting layer and operatingat least a second section of the controllable light-steering layer toselectively direct the second light toward a second periodic opticalfeature of the periodic optical layer, wherein the second periodicoptical feature focuses the second light onto the first voxel position.The first light and the second light may be emitted simultaneously orsynchronously or alternatively at different times in a time-multiplexedmanner. The method may further comprise, for at least a second voxel inthe image having a second voxel position, selectively emitting thirdlight by at least a third light-emitting element of the light-emittinglayer and operating at least a third section of the controllablelight-steering layer to selectively direct light toward a third periodicoptical feature of the periodic optical layer, wherein the thirdperiodic optical feature focuses the third light onto the second voxelposition. The first voxel position may have a first depth and the secondvoxel position may have a second depth different from the first depth.The light emitted by one of the plurality of light-emitting elements maybe steered toward one of the plurality of periodic optical featuresbased on depth information of the image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment.

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment.

FIG. 2 depicts light emission angles of a light field (LF) display.

FIG. 3A depicts a pair of eyes and the focus angle (FA) and convergenceangle (CA) produced by an LF display for a voxel formed at an LF displaysurface.

FIG. 3B depicts a pair of eyes and the FA and CA produced by an LFdisplay for a voxel formed behind an LF display surface.

FIG. 3C depicts a pair of eyes and the FA and CA produced by an LFdisplay for a voxel formed at an infinite distance behind the LF displaysurface.

FIG. 3D depicts a pair of eyes and the FA and CA produced by an LFdisplay for a voxel formed in front of an LF display surface.

FIG. 4A illustrates beam divergence caused by geometric factors of alens.

FIG. 4B illustrates beam divergence caused by diffraction.

FIG. 5 illustrates the image magnification for three lenses of differentoptical powers.

FIG. 6A illustrates the combined effects of geometric factors anddiffraction for one extended source and a small lens aperture.

FIG. 6B illustrates the combined effects of geometric factors anddiffraction for two sources and a small lens aperture.

FIG. 6C illustrates the combined effects of geometric factors anddiffraction for one source and a large lens aperture.

FIG. 6D illustrates the combined effects of geometric factors anddiffraction for two sources and large lens aperture.

FIG. 7 illustrates an example viewing geometry of a 3D light fielddisplay, in accordance with some embodiments.

FIG. 8A depicts a first example viewing geometry of a 3D LF display, inaccordance with some embodiments.

FIG. 8B depicts a second example viewing geometry of a 3D LF display, inaccordance with some embodiments.

FIG. 9 depicts a 3D LF display structure and its functionality, inaccordance with some embodiments.

FIG. 10A depicts a light concentrator used for changing the source NA,in accordance with some embodiments.

FIG. 10B depicts a light concentrator used for mixing colors of threeLEDs, in accordance with some embodiments.

FIG. 10C depicts a light concentrator used for mixing colors of fourLEDs with a smaller aperture structure, in accordance with someembodiments.

FIG. 11 is a representation of an example light-steering layerstructure, in accordance with some embodiments.

FIG. 12A is a first side view of a first periodic layer structurewherein the repeating periodic feature has three different zones withdifferent optical properties, in accordance with some embodiments.

FIG. 12B depicts a second periodic layer structure wherein a singleperiodic feature has a repeating pattern with nine zones, in accordancewith some embodiments.

FIG. 13 illustrates the spatial multiplexing function of an LF display,in accordance with some embodiments.

FIG. 14 depicts a display using crossing beams to form voxels, inaccordance with some embodiments.

FIG. 15 depicts a curved 3D light field display viewed from a distance,in accordance with some embodiments.

FIG. 16A is a representation of two light concentrators of alight-emitting layer, in accordance with some embodiments.

FIG. 16B is a representation of a source matrix of a light-emittinglayer, in accordance with some embodiments.

FIG. 17 is a representation of the optical design of a display, inaccordance with some embodiments.

FIG. 18 is an example of an optical ray trace diagram depicting lightfrom three source clusters traversing focusing lenses, light-steeringlayers, and a periodic layer.

FIG. 19 is a flowchart showing a method of displaying athree-dimensional image in accordance with some embodiments.

EXAMPLE NETWORKS FOR IMPLEMENTATION OF THE EMBODIMENTS

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, and so forth,to multiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN 104, aCN 106, a public switched telephone network (PSTN) 108, the Internet110, and other networks 112. The disclosed embodiments contemplate anynumber of WTRUs, base stations, networks, and/or network elements. Eachof the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d, any of which maybe referred to as a “station” and/or a “STA,” may be configured totransmit and/or receive wireless signals and may include user equipment(UE), a mobile station, a fixed or mobile subscriber unit, asubscription-based unit, a pager, a cellular telephone, a personaldigital assistant (PDA), a smartphone, a laptop, a netbook, a personalcomputer, a wireless sensor, a hotspot or Mi-Fi device, an Internet ofThings (IoT) device, a watch or other wearable device, a head-mounteddisplay (HMD), a vehicle, a drone, a medical device and applications(e.g., remote surgery), an industrial device and applications (e.g., arobot and/or other wireless devices operating in an industrial and/or anautomated processing chain contexts), a consumer electronics device, adevice operating on commercial and/or industrial wireless networks, andthe like. Any of the WTRUs 102 a, 102 b, 102 c and 102 d may beinterchangeably referred to as a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, anaccess point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and so forth. The base station 114 a and/or the base station 114b may be configured to transmit and/or receive wireless signals on oneor more carrier frequencies, which may be referred to as a cell (notshown). These frequencies may be in licensed spectrum, unlicensedspectrum, or a combination of licensed and unlicensed spectrum. A cellmay provide coverage for a wireless service to a specific geographicalarea that may be relatively fixed or that may change over time. The cellmay further be divided into cell sectors. For example, the cellassociated with the base station 114 a may be divided into threesectors. In one embodiment, the base station 114 a may include threetransceivers, e.g., one for each sector of the cell. In an embodiment,the base station 114 a may employ multiple-input multiple output (MIMO)technology and may utilize multiple transceivers for each sector of thecell. For example, beamforming may be used to transmit and/or receivesignals in desired spatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, and so forth). The air interface 116 may beestablished using any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by theWTRUs 102 a, 102 b, 102 c may be characterized by multiple types ofradio access technologies and/or transmissions sent to/from multipletypes of base stations (e.g., an eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b has a direct connection to theInternet 110. Thus, the base station 114 b may not be required to accessthe Internet 110 via the CN 106/115.

The RAN 104 may be in communication with the CN 106, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106 may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, the RAN 104 and/or the CN106 may be in direct or indirect communication with other RANs thatemploy the same RAT as the RAN 104 or a different RAT. For example, inaddition to being connected to the RAN 104, which may be utilizing a NRradio technology, the CN 106 may also be in communication with anotherRAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFiradio technology.

The CN 106 may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. The WTRU 102 may include anysub-combination of the foregoing elements while remaining consistentwith an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, the processor 118 and the transceiver 120 may be integratedtogether in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. The transmit/receiveelement 122 may be configured to transmit and/or receive any combinationof wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. For example, the WTRU 102 may employ MIMO technology.Thus, in one embodiment, the WTRU 102 may include two or moretransmit/receive elements 122 (e.g., multiple antennas) for transmittingand receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that aretransmitted by the transmit/receive element 122 and to demodulate thesignals that are received by the transmit/receive element 122. As notedabove, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134 and may beconfigured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),and so forth), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. The WTRU 102 may acquire location informationby way of any suitable location-determination method while remainingconsistent with an embodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102, for example, one or more of the WTRUs 102 a, 102 b, 102 c,102 d, may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) and DL(e.g., for reception) may be concurrent and/or simultaneous. The fullduplex radio may include an interference management unit to reduce andor substantially eliminate self-interference via either hardware (e.g.,a choke) or signal processing via a processor (e.g., a separateprocessor (not shown) or via processor 118). In an embodiment, the WTRU102 may include a half-duplex radio for which transmission and receptionof some or all of the signals (e.g., associated with particularsubframes for either the UL (e.g., for transmission) or the DL (e.g.,for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, although the RAN104 may include any number of eNode-Bs while remaining consistent withan embodiment. The eNode-Bs 160 a, 160 b, 160 c may each include one ormore transceivers for communicating with the WTRUs 102 a, 102 b, 102 cover the air interface 116. In one embodiment, the eNode-Bs 160 a, 160b, 160 c may implement MIMO technology. The eNode-B 160 a, for example,may use multiple antennas to transmit wireless signals to, and/orreceive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of these elements are depicted as partof the CN 106, any of these elements may be owned and/or operated by anentity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1C as a wireless terminal, insome embodiments, such a terminal may use (e.g., temporarily orpermanently) wired communication interfaces with the communicationnetwork.

In some embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In one or more embodiments, the DLS may use an 802.11e DLS or an 802.11ztunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may nothave an AP, and the STAs (e.g., all of the STAs) within or using theIBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In one or moreembodiments, Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) may be implemented, for example in in 802.11 systems. ForCSMA/CA, the STAs (e.g., every STA), including the AP, may sense theprimary channel. If the primary channel is sensed/detected and/ordetermined to be busy by a particular STA, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time ina given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to one embodiment,802.11ah may support Meter Type Control/Machine-Type Communications,such as MTC devices in a macro coverage area. MTC devices may havecertain capabilities, for example, limited capabilities includingsupport for (e.g., only support for) certain and/or limited bandwidths.The MTC devices may include a battery with a battery life above athreshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

One or more, or all, of the functions described herein with regard toone or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B 160 a-c, MME162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184 a-b, SMF 183a-b, DN 185 a-b, and/or any other device(s) described herein, may beperformed by one or more emulation devices (not shown). The emulationdevices may be one or more devices configured to emulate one or more, orall, of the functions described herein. For example, the emulationdevices may be used to test other devices and/or to simulate networkand/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

DETAILED DESCRIPTION

Systems and methods are described for providing a 3D display, such as alight-field display. In some embodiments, an optical method andconstruction of an optical system generates high-resolution 3D LF imageswith crossing light beams. Light is emitted from a layer containingindividually addressable sources or pixels, for example, a μLED matrixor an OLED display. A converging lens structure, for example, apolycarbonate lenticular sheet, overlays the emitters. The converginglens structure focuses the light into a set of beams. Separatelight-steering layers or elements may be used to tilt the beams towardsspecific locations on a periodic optical layer. In some embodiments,non-mechanical beam steering components, for example, hybrid structuresincluding liquid crystal materials and polymer microprism sheets basedon polarization switching or electrowetting microprisms, may be used.Periodic layer features may be configured to change the focus distanceof each beam and may be utilized to create a series of fixed focalplanes. The periodic layer may be manufactured, for example, as apolycarbonate sheet with optical shapes made from UV-curable material ora thin sheet with embossed diffractive structures. In some embodiments,spatial multiplexing in the LF display system may be provided by usingprojector cells containing multiple light sources. Temporal multiplexingmay be provided by using light-steering layers for switching betweendifferent projected focal distances.

In some embodiments, the optical system may use crossing beams to formvoxels. In some embodiments, voxels may be formed at discrete distancesfrom the surface of the display. Voxels may be formed, for example, infront of, behind, and/or on the display surface. Emitted beams may focusto different distances from the optical structure and image the sourcesin different sized areas depending on the distance. Single beams may beused for generating the correct retinal focus cues for single eyes.Multiple beams crossing at the correct voxel distance may be used togenerate the full voxel for two eyes and for inducing the correct eyeconvergence angles. The retinal focus cues and convergence angles may becreated separately. This configuration may overcomevergence-accommodation conflict (VAC). The source matrix, focusinglenses, light-steering layers, and periodic layer may be configured toform a system capable of generating several virtual focal surfaces intothe 3D space around the display.

In some embodiments, an optical method is based on the use of one ormore light-steering layers or elements and periodic focusing layer.Light is emitted from separately controllable small emitters. An opticallayer may be used to collimate or converge the light into beams. In someembodiments, the optical layer includes microlenses. A combination oflight-steering layers and a periodic layer of optical features may beused for focusing beams to multiple focal layers. Two or more crossingbeams may be used for initiating eye convergence. This configuration mayform voxels without contradicting focus cues.

Some embodiments provide the ability to create a display, such as alight field (LF) display, that is capable of presenting multiple focalplanes of a 3D image while overcoming the vergence-accommodationconflict (VAC) problem. Some embodiments provide the ability to create adisplay, such as a light field display with thin optics, without theneed for moving parts. In some embodiments, the non-mechanical beamsteering layers may be produced using liquid crystal technology.

In some embodiments, a method includes altering the focal depth of alight projection using beam steering optical elements and a periodic orrepeating focusing layer.

Some embodiments provide a display capable of producing images atmultiple focal planes with the use of a periodic optical structurewithout the need for a spatial light modulating layer in front of theoptics. Some such embodiments may reduce complexity of the opticalhardware and/or electronics. Such embodiments may allow for betteroptical efficiency and energy savings than, for example, configurationsutilizing a spatial light modulator that acts as an adaptive mask andattenuates a significant amount of light.

FIG. 2 depicts various light emission angles directed towards respectiveviewers or users. For example, FIG. 2 shows a view of the geometry oflight emission angles from a LF display 200 for a virtual object point202. The display/touchpad 128 may comprise the LF display 200. The LFdisplay 200 in FIG. 2 produces the desired retinal focus cues andmultiple views of 3D content in a single flat form-factor panel. Asingle 3D display 200 projects at least two different views to the twoeyes of a single user 212 in order to create a coarse 3D perceptioneffect. The brain uses these two different eye images to determine 3Ddistance. Logically this is based on triangulation and interpupillarydistance. To provide this effect, at least two views are projected intoa single-user viewing angle (SVA) 204, as shown in FIG. 2 . In at leastone embodiment, the LF display 200 projects at least two different viewstoward a single eye pupil in order to provide correct retinal focuscues. For optical design purposes, an eye-box may be characterizedaround the viewer eye pupil when determining the volume of space withinwhich a viewable image is formed. See, for example, the eye-box width206 shown in FIG. 2 . In some embodiments of the LF display 200, atleast two partially overlapping views are projected inside an Eye-BoxAngle (EBA) 208 covered by the eye-box at a known viewing distance 214.In some embodiments, the LF display 200 is viewed by multiple viewers212 looking at the display from different viewing angles. In suchembodiments, several different views of the same 3D content areprojected to viewers 212 covering a whole intended Multiuser ViewingAngle (MVA) 210.

FIG. 2 illustrates that an LF display 200 may advantageously cover threedifferent angular ranges simultaneously: one range for covering thepupil of a single eye, one range for covering the two eyes of a singleuser, and one range for multiple viewers 212. Of these three angularranges, the latter two may be resolved, for example, by using severallight-emitting pixels under a lenticular or parallax barrier structureor by using several projectors with a common screen. Such techniques maybe suitable for the creation of relatively large light emission anglesutilized in the creation of multiple views. Addressing the rangecovering the eye pupil in order to produce the correct retinal focuscues and overcome vergence-accommodation conflict (VAC) may produce moreadvantageous results.

VAC is one issue with current stereoscopic 3D displays. A flatform-factor LF 3D display may address this issue by producing both thecorrect eye convergence and correct focus angles simultaneously. Incurrent consumer displays, an image point lies on a surface of adisplay, and only one illuminated pixel visible to both eyes is neededto represent the point correctly. Both eyes are focused and converged tothe same point. In the case of parallax-barrier 3D displays, twoclusters of pixels are illuminated to represent the single pointcorrectly. In addition, the direction of the light rays from these twospatially separated pixel clusters are controlled in such a way that theemitted light is visible only to the correct eye, thus enabling the eyesto converge to the same single virtual point.

A flat form-factor high-quality LF 3D display able to produce both theeye convergence (CA) angles 318 and retinal focus (FA) angles 320simultaneously may provide a more desirable effect. FIG. 3A through FIG.3D show these angles 318, 320 in four different 3D image content cases.In the first case illustrated in FIG. 3A, the single image point 304 ison the surface of the LF display 200 and only one illuminated displaypixel visible to both eyes 302 is needed. Both eyes are focused andconverged on the same point 304. In the second case as illustrated inFIG. 3B, where the virtual image point (voxel) 306 is behind the LFdisplay 200 and two clusters of pixels 308 are illuminated. In addition,the direction of the light rays from these two display pixel clusters308 are controlled in such a way that the emitted light is visible onlyto the correct eye, thus enabling the eyes to converge to the samesingle virtual point 306. In the third case as illustrated in FIG. 3C,the virtual image converges effectively at an infinite distance 310behind the screen and only parallel light rays or beams 322 are emittedfrom the display surface from two pixel clusters 312. In the last caseas illustrated in FIG. 3D, the image point or voxel 314 is in front ofthe display, two pixels clusters 316 are activated, and the emittedbeams cross at the same point 314 where they focus. In the last threepresented generalized cases, both spatial and angular control of emittedlight is used by the LF display 200 in order to create both theconvergence angles 318 and focus angles 320 for natural eye responses tothe 3D image content.

A flat-panel-type multi-view LF display 200 may implement spatialmultiplexing alone. A row or matrix of light-emitting pixels (LFsub-pixels) may be located behind a lenticular lens sheet or microlensarray, and each pixel may be projected to a unique view direction or toa limited set of view directions in front of the display structure. Asmore pixels are present on the light-emitting layer behind each lightbeam collimating or converging feature, the more views can be generated.A trade-off may be found between the number of unique views generatedand spatial resolution. If a smaller LF pixel size is desired from the3D display, the size of individual sub-pixels may be reduced; oralternatively, a smaller number of viewing directions may be generated.Sub-pixel sizes may be limited to relatively large areas due to lack ofsuitable components. A high-quality LF display 200 having both highspatial and angular resolutions is desirable. High angular resolution isdesirable in fulfilling the SMV condition.

In order to produce 3D LF images at different focal planes withsufficient resolution by utilizing crossing beams, each beam isadvantageously well-collimated or converged with a narrow diameter. Insome embodiments, the level of collimation or convergence is related tothe position of the focal plane being displayed. For example, beams maybe substantially collimated or converged but slightly diverging fordisplay of focal planes behind the display, and beams may besubstantially collimated but slightly converging for display of focalplanes in front of the display.

The beam waist may advantageously be positioned at the same area wherethe beams cross to avoid contradicting focus cues for the eye. If thebeam diameter is large, the voxel formed in the beam crossing is imagedto the eye retina as a large spot or area. A large divergence value (foran intermediate image between the display and viewer) results in thebeam becoming wider as the distance between the voxel and the eye getssmaller. With smaller distances, the eye resolves images in higherdetail. The spatial resolution of the virtual focal plane becomes worse,however, with smaller distances. Voxels positioned behind the displaysurface are formed with virtual extensions of the emitted beams, andwider beams may be acceptable because the eye's resolution also becomesworse at longer distances. In order to have high resolution both infront of and behind the display surface, separate beams with adjustablefocuses may be utilized. Without adjustable focus, the beams have asingle fixed focus that sets the smallest achievable voxel size. Becausethe eye resolution is lower at larger distances, the virtual extensionsof the beams may be allowed to widen behind the display and the beamfocus may be set to the closest specified viewing distance of the 3Dimage. In some embodiments, the focal surface resolutions may also bebalanced throughout the volume, where the image is formed by combiningseveral neighboring beams in an attempt to make the voxel sizes uniform.

In the case of an ideal lens, the achievable light beam collimation isdependent on two geometrical factors: size of the light source and focallength of the lens. Perfect collimation 408 without any beam divergencecan only be achieved in the theoretical case in which a single-colorpoint source (PS) 402 is located exactly at focal length distance froman ideal positive lens, such as shown at the top of FIG. 4A.Unfortunately, real-life light sources have a finite surface area fromwhich the light is emitted, making them extended sources (ES) 404. Aseach point of the source is separately imaged by the lens, the totalbeam ends up as a group of collimated or converged sub-beams thatpropagate along somewhat different directions after or beyond the lens.As presented in FIG. 4A, a smaller extended source 404 has a smallertotal beam divergence 410, whereas a larger extended source 406 has alarger total beam divergence 412, thus total beam divergence increaseswith the size of the extended source. This geometrical factor cannot beavoided with any optical means and is the dominating characteristiccausing beam divergence with relatively large light sources.

Another, non-geometrical, feature causing beam divergence isdiffraction. Diffraction includes various phenomena that occur when awave of light encounters an obstacle or a slit. It can be described asthe bending of light around the corners of an aperture into the area ofgeometrical shadow. Diffraction effects can be found in all imagingsystems and cannot be removed even with a perfect lens design that isable to balance out all optical aberrations. A lens that is able toreach the highest optical quality is often called diffraction limitedbecause most of the blurring remaining in the image comes fromdiffraction. The angular resolution achievable with a diffractionlimited lens can be calculated from the formula sin θ=1.22*λ/D, where λis the wavelength of light and D the diameter of the entrance pupil ofthe lens. Thus, the color of light and lens aperture size have aninfluence on the amount of diffraction. FIG. 4B shows a representationof how the beam divergence is increased when the lens aperture size isreduced. This effect can be formulated into a general principle inimaging optics design: if the design is diffraction limited, the way toimprove resolution is to make the aperture larger. Diffraction is thedominating feature causing beam divergence with relatively small lightsources.

As shown in FIG. 4A, the size of an extended source has a big effect onthe achievable beam divergence. The source geometry or spatialdistribution is mapped to the angular distribution of the beam as can beseen in the resulting far field pattern of the source-lens system. Ifthe collimating or converging lens is positioned at a focal distancefrom the source, the source is imaged to a relatively large distancefrom the lens, and the size of the image can be determined from thesystem magnification ratio. In the case of a simple imaging lens, thisratio can be calculated by dividing the distance between lens and imageby the distance between source and lens as illustrated in FIG. 5 . Ifthe distance between source and lens is fixed, different image distancescan be achieved by changing the optical power of the lens with the lenscurvature. As the image distance becomes larger in comparison to thelens focal length, the required changes in lens optical power becomesmaller, approaching the situation where the lens effectively collimatesor converges the emitted light into a beam that has the spatialdistribution of the source mapped into the angular distribution, and thesource image is formed without focusing.

In flat form factor goggleless LF displays, the LF pixel projectionlenses may have very small focal lengths in order to achieve the flatstructure and in order to allow the beams from a single LF pixel to beprojected to a relatively large viewing distance. Thus, the sources maybe effectively imaged with high magnification when the beams of lightpropagate to the viewer. For example, if the source size is 50 μm×50 μm,projection lens focal length is 1 mm, and viewing distance is 1 m, theresulting magnification ratio is 1000:1, and the source geometric imageis 50 mm×50 mm in size. As a result, the single light emitter can beseen only with one eye inside this 50 mm diameter eye-box. If the sourcehas a diameter of 100 μm, the resulting image would be 100 mm wide andthe same pixel could be visible to both eyes simultaneously, because theaverage distance between eye pupils is only 64 mm. A stereoscopic 3Dimage would not be formed because both eyes would see the same image(s).The example calculation shows how the geometrical parameters such aslight source size, lens focal length, and viewing distance are relatedto each other.

As the beams of light are projected from the LF display pixels,divergence causes the beams to expand. This divergence applies not onlyto the actual beam emitted from the display towards the viewer, but alsoto the virtual beam that appears to be emitted behind the display,converging to the single virtual focal point close to the displaysurface. In the case of a multi-view display, this divergence may beuseful because the divergence expands the size of the eye-box. Providinga beam size that does not exceed the distance between the two eyes maybe utilized to break the stereoscopic effect. When creating a voxel in avirtual focal plane with two or more crossing beams anywhere outside thedisplay surface, the spatial resolution achievable with the beamsreduces as the divergence increases. If the beam size at the viewingdistance is larger than the size of the eye pupil, the pupil becomes thelimiting aperture of the optical system.

Geometric and diffraction effects are utilized in the LF display'sdesign in order to achieve an optimal solution for voxel resolution.With very small light sources, optical system measurements become closerto the wavelength of light and diffraction effects become moresignificant. FIG. 6A through FIG. 6D illustrate examples of how thegeometric and diffraction effects work together in situations where oneand two extended sources are imaged to a fixed distance with a fixedmagnification. FIG. 6A depicts a lens 602 where the lens aperture sizeis relatively small, 5 μm, and the Geometric Image (GI) 604 issurrounded by blur that comes from diffraction, making the DiffractedImage (DI) 606 much larger. FIG. 6B shows two extended sources 404placed side-by-side and imaged with the same small aperture, 5 μm, lens.Even though the GIs 608, 610 of both sources 404 are clearly separated,the two source images cannot be resolved because the diffracted images612, 614 overlap. In practice, reducing light source size would notimprove the achievable voxel resolution because the resulting sourceimage size would be the same whether two separate light sources or onelarger source that covers the area of both separate emitters is used. Toresolve the two source images as separate pixels/voxels, increasing theaperture size of the imaging lens may be advantageous. FIG. 6C shows thesame focal length lens 616, but with a larger aperture, 5 μm, used inimaging the extended source 404. In this situation, the diffraction isreduced, and the DI 620 is only slightly larger than the GI 618, whichhas not changed e because magnification is fixed. In FIG. 6D, the twoGIs 622, 624 can now be resolved because the Dis 626, 628 are no longeroverlapping. In this configuration, use of two different sourcesimproves the spatial resolution of the voxel grid.

Optical Design Features of LF Displays Based on Crossing Beams

Some embodiments provide the ability to create a display. In someembodiments, the display may be used as a light field display 200 thatis capable of presenting multiple focal planes of a 3D image whileaddressing the vergence-accommodation conflict (VAC) problem.

In some embodiments, the LF display 200 projects emitter images towardsboth eyes of the viewer without light scattering media between the 3Ddisplay and the viewer. In order to create a stereoscopic image bycreating a voxel located outside the display surface, the LF display 200may be configured such that an emitter inside the display associatedwith that voxel is not visible to both eyes simultaneously. Accordingly,the field-of-view (FOV) of an emitted beam bundle may cover both eyes.The single beams may have FOVs that are narrower than the distancebetween two eye pupils (e.g., ˜64 mm on average) at the viewingdistance. The FOV of one display section as well as the FOVs of thesingle emitters may be affected by the widths of the emitter row/emitterand magnification of the imaging optics. A voxel created with a focusingbeam may be visible to the eye only if the beam continues itspropagation after the focal point and enters the eye pupil. The FOV of avoxel may advantageously cover both eyes simultaneously. If a voxel werevisible to single eye only, the stereoscopic effect may not be formed,and a 3D image may not be seen. Because a single display emitter may bevisible to only one eye at a time, increasing the voxel FOV by directingmultiple crossing beams from more than one display emitter to the samevoxel within the human persistence-of-vision (POV) time frame may beadvantageous. In some embodiments, the total voxel FOV is the sum ofindividual emitter beam FOVs.

For local beam bundle FOVs to overlap at their associated specifiedviewing distances, some embodiments may include a curved display 702with a fixed radius. In some embodiments, the projected beam directionsmay be directed towards a specific point, for example, using a flatFresnel lens sheet. If the FOVs were not configured to overlap, someparts of the 3D image may not be formed. Due to the practical sizelimits of a display and practical limits for possible focal distances,an image zone may be formed in front of and/or behind the displaycorresponding to the region wherein the 3D image is visible. FIG. 7 is arepresentation of an example viewing geometry that may be achieved witha 3D LF display 702 using crossing beams. In front of the curved display702, the edge of a 3D image zone 704 maybe the furthest focal distancefrom the display with reasonable spatial resolution. The image zone 704may also be limited by the FOV 708 of the whole display 702. To get themaximum resolution at the minimum image distance 714, the opticalfeatures of the display 702 may be designed to focus the source imagesto the furthest edge of this image zone 704. In some embodiments,another image zone 706 behind the display may be formed by the virtualextensions of the emitted beams. In some embodiments, voxels behind thedisplay 702 may have larger allowable sizes because the viewer ispositioned further away and because eye resolution may be lower atgreater distances. In some embodiments, a maximum image distance 718 maybe selected based on a minimum acceptable resolution achievable with thebeam virtual extensions.

FIG. 7 depicts an example viewing geometry of a 3D light field display,in accordance with some embodiments. The surface of the display 702depicted in FIG. 7 is curved with a radius that is the same as thedesignated viewing distance 716. In the example, the overlapping beambundle FOVs form a viewing zone 710 around the facial area of the viewer712. The size of this viewing zone 710 may affect the amount of movementallowed for the viewer's head. Both eye pupils positioned inside thezone simultaneously make the stereoscopic image possible. The size ofthe viewing zone may be selected by altering the beam bundle FOVs. FIG.8A and FIG. 8B show a representation of two different example viewinggeometry cases. As shown in FIG. 8A, a single viewer 802 is shown infront of a display 702 with the corresponding viewing geometry, whereina small viewing zone 804 covers both eyes' pupils, which may be achievedusing narrow beam bundle FOVs 806. A minimum functional width of theviewing zone 804 may be affected by the eye pupil distance. For example,an average pupil distance 720 may be ˜64 mm, such as shown in FIG. 7 . Asmall width may also imply a small tolerance for viewing distancechanges as narrow FOVs tend to quickly separate from each other atincreasing distances both in front of and behind the optimal viewinglocation. A viewing geometry with wider beam bundle FOVs 808 is shown inFIG. 8B. This viewing geometry may facilitate multiple viewers 802inside the larger viewing zone 810 and/or at different viewingdistances. In this example, positional tolerances may be large.

The viewing zone may be increased by increasing the FOV of each displaybeam bundle. For example, increasing the width of the light emitter rowor by changing the focal length of the beam collimating or convergingoptics may increase the FOV. Smaller focal lengths may result in largervoxels, thus increasing the focal length may achieve better resolution.A trade-off may be found between the optical design parameters and thedesign needs. Accordingly, different use cases may balance between thesefactors differently.

Technological Status of μLED Sources in Display Applications

Some embodiments utilize μLEDs. μLEDs are LEDs that are manufacturedwith the same basic techniques and from the same materials as standardLEDs, but μLEDs are miniaturized versions of the commonly availablecomponents and can be made as small as 1 μm to 10 μm in size. Oneexample of a dense matrix has 2 μm×2 μm chips assembled with 3 μm pitch.μLEDs have been used as backlight components in TVs. When compared toOLEDs, μLEDs are much more stable components and can reach very highlight intensities.

A bare μLED chip may emit a specific color with spectral width of ˜20-30nm. A white source can be created by coating the chip with a layer ofphosphor that converts the light emitted by blue or UV μLEDs into awider white light emission spectrum. A full-color source can also becreated by placing separate red, green, and blue μLED chips side-by-sidebecause the combination of these three primary colors creates thesensation of a full color pixel when the separate color emissions arecombined by the human visual system. The previously mentioned densematrix facilitates the manufacturing of self-emitting full-color pixelsthat have a total width below 10 μm (3×3 μm pitch).

Light extraction efficiency from the semiconductor chip is one of theparameters that determine electricity-to-light efficiency of LEDstructures. Several methods aim to enhance the extraction efficiency andthus facilitate LED-based light sources to use the available electricenergy as efficiently as feasible, which is useful with, for example,mobile devices that have a limited power supply. Some methods utilize ashaped plastic optical element that is integrated directly on top of anLED chip. Due to lower refractive index difference, integration of theplastic element extracts more light from the chip material in comparisonto a chip surrounded by air. The plastic element also directs the lightin a way that enhances light extraction from the plastic element andrenders the emission pattern to be more directional. Other methods, suchas the methods found in U.S. Pat. No. 7,518,149, shape the chip itselfinto a form that favors light emission angles that are moreperpendicular towards the front facet of the semiconductor chip and thelight more easily escape the high refractive index material. Thesestructures also direct the light emitted from the chip. In the lattersituation, the extraction efficiency was estimated to be twice as highwhen compared to regular μLEDs. Considerably more light was emitted byan emission cone of 30° in comparison to a standard chip Lambertiandistribution where light is distributed evenly to the surroundinghemisphere.

Non-Mechanical Beam Steering Components in 3D Display Applications

In some embodiments, electrowetting cells may be implemented fornon-mechanical beam steering. Electrowetting cells may be configured toform tunable microprisms that can be used to provide continuous scanningof beams through a relative large angular range (e.g. ±7°) with highswitching speeds (˜ms), for example, by using the techniques discussedin Neil R. Smith, Don C. Abeysinghe, Joseph W. Haus, and JasonHeikenfeld, “Agile wide-angle beam steering with electrowettingmicroprisms,” Optics Express Vol. 14, Issue 14, pp. 6557-6563, (2006).Polarization independence provided by the electrowetting cell approachmay be useful for achieving higher optical efficiencies for thecomponents. Electrowetting cells may be implemented in some embodimentsusing techniques including, for example, the techniques found inCanadian Patent CA2905147 for switching between 2D and 3D display modes,and the techniques found in WO2008142156 for beam steering in adirectional backlight system. In some embodiments, electrowetting may beimplemented for forming lenticular structures of a multi-view displaysystem, for example, by using the techniques described in J. Kim, D.Shin, J. Lee, G. Koo, C. Kim, J-H. Sim, G. Jung, Y-H. Won,“Electro-wetting lenticular lens with improved diopter for 2D and 3Dconversion using lens-shaped ETPTA chamber,” Opt. Express 26, No. 15,19614-19626 (2018).

In some embodiments, components and systems based on utilization ofliquid crystal (LC) materials are implemented for non-mechanical beamsteering. As highly birefringent material, the LC layers have differentrefractive indices in two orthogonal directions. This property may beuseful when implemented along with polymer microprisms, for example, byusing the techniques as described in H. Wang, O. Yaroshchuk, X. Zhang,Z. Zhuang, P. Surman, X. Wei Sun, Y. Zheng, “Large-aperture transparentbeam steering screen based on LCMPA,” Applied Optics Vol. 55, Issue 28,(2016). As described in H. Wang, et all (2016), the polymer microprismsare used for switching between two beam steering states with a structurethat contains two LC layers. A first, active LC layer, is sandwichedbetween, for example, two glass sheets containing electrodes. A second,passive layer, is formed between a glass or polymer substrate and apolymer microprism sheet. Switching is initiated with the active LClayer that twists incident beam linear polarization by 90° in theperpendicular direction to light propagation when voltage is applied.This twisting selects which of the refractive indices of thebirefringent passive LC layer is used in the second part of the system.In a first state of the steering system, refractive index differencebetween passive LC layer and microprism polymer material is so smallthat no light bending occurs, whereas in a second state, the indexdifference causes light rays to bend to a predetermined angle at theinterface. This angle is usually small (˜1°), but can be increased, insome embodiments, by employing various techniques. For example, rays oflight may be bent to larger angles by, e.g., adding holographic gratingsafter the LC layers, for example, by using the techniques described inP. McManamon, P. Bos, M. Escuti, J. Heikenfeld, S. Serati, H. Xie, E.Watson, “A Review of Phased Array Steering for Narrow-BandElectrooptical Systems,” Proceedings of the IEEE, Vol 97, Issue 6,(2009). Another way the angle may be increased, in some embodiments, isby stacking several polarization-based beam steering components,reaching angles as large as, for example, ±15°, as described, forexample, in WO2011014743.

Liquid crystal displays (LCDs) have been used for several decades by thedisplay industry. After such a long history of research, LCD materialproperties and processing methods are very well known. One advantage ofLC-based beam steering methods is that the components may be producedfairly easily with currently available manufacturing technology andequipment, making low-cost manufacture in large quantities possible.Needing no mechanical movement to initiate beam steering is also afactor in favor of using such technologies in 3D displays. Disadvantagesof the use of linearly polarized light are lowered optical efficiency ofthe system and increased power consumption. Because current LCD displaysare already polarization dependent systems, new steering components maybe integrated more easily without high cost in efficiency. In addition,some embodiments may make use of cholesteric LCs, instead of the morecommon nematic phase crystals, which can be used for beam steeringwithout polarization dependence. The use of cholesteric LCs may beimplemented, for example, by using techniques such as discussed in ShangX, Meeus L, Cuypers D, De Smet H, “Fast switching cholesteric liquidcrystal optical beam deflector with polarization independence,”Scientific Reports, July 26, 7(1):6492, (2017). Such embodiments mayincrease the component transmittance for display panels comprising, forexample, OLEDs or μLEDs.

LC components may be implemented in some embodiments as electricallyswitchable parallax barriers, for example, by using the techniquesdiscussed in U.S. Pat. No. 9,664,914, wherein a black grating structureis implemented to block some display pixel view directions when the LClayer is activated. This configuration may produce different images thatcan be shown to both eyes of the viewer. Without the activated grating,the display may function as a normal 2D display. The LC layer may alsobe used in forming a lenticular lens structure on top of a dense pixelmatrix by reorienting some of the LC material molecules with electriccurrent by using, for example, the techniques discussed in U.S. Pat. No.9,709,851. Such a configuration may utilize special electrode designs,but can also be used for switching between 2D and 3D modes because theLC lenses project the pixel images to different view directions. In the3D mode, multiple views may be obtained with the cost of lower spatialresolution because only spatial multiplexing is used in creation of themulti-view image. Some embodiments may employ scanning the electricallyformed lenticular LC lenses through the display surface, usingtechniques such as those discussed in Y-P. Huang, C-W. Chen, T-C. Shen,J-F. Huang, “Autostereoscopic 3D Display with Scanning Multi-ElectrodeDriven Liquid Crystal (MeD-LC) Lens,” 3D Research, Vol. 1, Issue 1, pp39-42, (2010). Such embodiments may facilitate time multiplexing. Forexample, the pixels synchronized to the scanning action may be activatedseveral times inside a single scan timeframe, creating severaladditional views. Some embodiments may employ hybrid systems, where beamsteering LC element is used before or after a rigid polymer lenticularsheet structure. Examples of such hybrid systems are discussed inWO2012025786 and Xiangyu Zhang, Hongjuan Wang, Phil Surman, YuanjinZheng, “A Novel Spatio-temporal Multiplexing Multi-view 3D Display,”IEEE Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR),(2017). Such hybrid systems may facilitate the creation of additionalangular view directions between the directions determined by pixelpositions and lenticular optics. In some such embodiments, temporalmultiplexing may be used along with spatial multiplexing in 3Dmulti-view displays. In some embodiments, LC-based beam steering screencomponents may be used in a similar manner with multiple projectors, forexample by using the techniques discussed in X. Xia, X. Zhang, L. Zhang,P. Surman, and Y. Zheng, “Time-multiplexed Multi-view Three-dimensionalDisplay with Projector Array and Steering Screen,” Optics Express Vol.26, Issue 12, pp. 15528-15538, (2018).

In addition to beam angular steering, both the electrowetting cells andLC based components with hybrid structures can be used for adjustingbeam focus without mechanical movement. Examples of electrowetting cellsthat may be implemented in some embodiments include those discussed inU.S. Pat. No. 6,369,954 and in K. Mishra, H. van den Ende, F. Mugele,“Recent Developments in Optofluidic Lens Technology,” Micromachines7(6):102, (2016). Examples of hybrid structures that may be implementedin some embodiments are discussed in U.S. Pat. Nos. 7,408,601,9,709,829, and WO2016135434.

In some embodiments, electronic focus adjustment may be utilized in headmounted devices, for example, wherein a stereoscopic 3D display virtualimage can be moved to different focal distances from the eye, forexample, by using the techniques discussed in G. Love, D. Hoffman, P.Hands, J. Gao, A. Kirby, and M. Banks, “High-speed switchable lensenables the development of a volumetric stereoscopic display,” OptExpress, 17(18): 15716-15725, (2009). In this manner, images may be madeto look more natural. In some embodiments, beam focus adjustment may beutilized in goggleless 3D displays, for example, by adjusting theposition or shape of the projected image focal surface as described inN. Matsuda, A. Fix, D. Lanman, “Focal Surface Displays,” ACMTransactions on Graphics 36(4):1-14, (2017). In embodiments describedherein, focus adjustment may provide the ability to alter a wholeprojected image or to adjust the focus of multiple beams individually.

Example Optical Structure and Function

Some embodiments provide an optical method and apparatus of an opticalsystem that may be used for creating high-resolution 3D LF images withcrossing beams. FIG. 9 depicts a light generation module 900 of a 3D LFdisplay 200, in accordance with some embodiments. As shown in theexample in FIG. 9 , light is emitted from a light-emitting layer 902with separately controllable light emitters 904, 906, 908, 910, 912,914, 916, such as μLEDs. A converging lens structure or layer 920, forexample, a polycarbonate microlens sheet, overlaying the emitters of thelight-emitting layer 902 collects and focuses the light into a set ofbeams that are used to form an image in different viewing directions.The converging lens layer 920 may comprise an array of converging lenses923. The array may be a two-dimensional array of lenses 944, and eachconverging lens 944 may be associated with at least one of thelight-emitting elements 908 in a projector cell 946. Each emitter andits corresponding converging lens are components in a projector cell946. Adjacent projector cells may be separated from each other withopaque baffle structures (not illustrated) that suppress crosstalk. Ifnon-polarized light sources such as μLEDs or OLEDs are used, a polarizer918 may be added to obtain linearly polarized beams. When an LCD panelsource is utilized, polarizers may be integrated to the source componentsuch that no additional polarizers 918 are needed.

FIG. 9 illustrates light-steering layers 922, 924 and a periodic opticallayer 926 also referred to as a periodic layer 926. In some embodiments,the periodic layer 926 is continuous. The periodic layer 926 may overlaythe light-steering layers 922, 924 and the light-emitting layer 902. Thelight or beam steering layers 922, 924 may tilt or alter the directionsof light or beams coming from the light generation module 900. The oneor more light-steering layers 922, 924 may be controllable as describedbelow. These beams may be steered to specific locations or positions onthe periodic layer 926. Periodic features 928, 930, 932 on one surfaceof the periodic layer 926 may change the focus distance of each beam indifferent ways, thereby generating a series of fixed focal planes wherelayers of a 3D image are formed with crossing beams. The periodicfeatures 928, 930, 932 have at least one different optical property fromone another, for example, refractive index, light scattering, and asurface property, such as shape or radius of curvature. In the exampleof FIG. 9 , a first light source 910 positioned at the middle of thestructure is focused to the front of the whole display structure thougha flat feature 928 on the periodic layer and through the steering layers922, 924 that are not activated. The first light source 910 is imaged toa focal point 934 directly on the display surface. Another light source906, above the first light source 910, generates another focused beamthat is tilted at an angle 936 by the light-steering layers 922, 924toward another feature 930 of the periodic layer 926. This feature 930has negative optical power that extends the beam focal distance in sucha way that the beam appears to be emitted from a focal point 938 behindthe display 200. A third emitter 914, below the first light source 910,generates a beam that is tilted at another angle 940. This beam isfocused on a second type of negative optical power feature 932 on theperiodic layer 926, causing the beam to focus at a focal point 942 infront of the display 200. One or more of the focus-changing opticalfeatures 930, 932 on the periodic layer 926 may be configured to haveadditional tilts with respect to the beam optical axis in order tocompensate for the beam directional changes in the light-steering layers922, 924. In this manner, different focal distance beams may beprojected from a single source towards the viewer. The light-steeringlayers 922, 924 may therefore be used to switch between differentprojected focal distances, thereby adding temporal multiplexing to theLF display system.

In some embodiments, source components in the light-emitting layer mayinclude μLEDs provided with molded light concentrator structures, suchas polymer light concentrator structures, as described herein. In someembodiments, a concentrator 1002 collects light emitted from a source1004 to a large numerical aperture (NA) 1006 and concentrates the lightto a smaller NA 1008. FIG. 10A depicts a light concentrator 1002 thatchanges the source NA, in accordance with some embodiments. In theexample of FIG. 10A, NA 1008 is smaller than NA 1006. In someembodiments, light concentrators mix colors, for example, when separatered 1014, green 1016, and blue 1018 components are utilized. FIG. 10Bdepicts a light concentrator 1010 with a mixer 1012 that mixes colors ofthree LEDs 1014, 1016, 1018, in accordance with some embodiments. Inthese types of concentrators, one part 1010 of the structure may providelight concentration and another part 1012 provides spatial mixing of thedifferent colored light, resulting in a mixed RGB output 1020. Spatialmixing may be useful in LF systems where the spatial position of thesource causes an angular direction. Without mixing, color separation inthe voxels may result. As angular spread decreases in the concentrator,the size of the optical aperture increases. Increased optical aperturemay have a negative effect on LF systems using spatial multiplexingwhere smaller pixel sizes are desired. FIG. 10C depicts a lightconcentrator used for mixing colors of four LEDs, such as an LEDcluster, 1022 with a smaller aperture structure 1024, in accordance withsome embodiments. In the example of FIG. 10C, the sources 1022 aregrouped into a square pattern as shown in the side view 1026 and overmolded into a joint concentrator 1028 and mixer 1030 that outputs mixedRGB light 1032. In this example, the front or input surface of the lightconcentrator is curved to improve the NA concentration. This surface canalso be tilted in order to tilt the light output to an off-axis angle.

FIG. 11 is a representation of an example light-steering layer structure922, 924 of the light generation module 900 of an LF display 200, inaccordance with some embodiments. In the example, two light-steeringlayers 922, 924 bend beam paths in two different directions at twodifferent angles 936, 938. One beam steering layer may be used toswitch, for example, between two angles, but two cascaded layers maygenerate at least three different steering states. As an example, FIG.11 shows three different ray paths 1102, 1104, and 1106. For the firstpath 1102, the first beam steering layer 922 is made transparent to thelight ray, while the second layer 924 tilts the propagation direction byan angle 936. For the second path 1106, the first element tilts thepropagation direction by an angle 940. The middle ray path 1104,experiences no directional changes because both steering layers are madetransparent, for example, by suitable twisting of the linearpolarization directions in both active LC layers. A combination of thetilting directions is also possible with suitable LC layer arrangements.In some embodiments, more than two elements are stacked in order toproduce a greater number of discrete steering angles.

Each light-steering layer 922, 924 shown in FIG. 11 has two thin glasssubstrate layers 1108, 1118, 1110, 1120, that act as support materialfor the first LC layer 1112, 1122. This active LC layer 1112, 1122 mayact as a polarization modulator. The light-steering layers 922, 924 maybe controllable, for example, by applying voltages to the electrodes ofone or more of the light-steering layers 922, 924. The electrodes may beadvantageously be transparent, for example, comprising indium tin oxide.Each projector cell 946 may be associated with a different section ofone or more of the light-steering layers 922, 924. Each section of theone or more of the light-steering layers 922, 924 may be separatelycontrolled or controllable. When voltage is applied to the transparentelectrodes patterned on the glass substrates 1108, 1118, 1110, 1120, theLC layer may become transparent to linearly polarized light such thattransmitted beams remain unchanged. When no voltage is applied to thefirst LC layer 1112, 1122, it acts as a polarization rotator by rotatingthe polarization direction by 90° normal to the propagation direction.As shown in FIG. 11 , a second, passive LC layer 1114, 1124 issandwiched between the second glass substrate 1110, 11120 and amicroprism, such as a polymer microprism layer 1116, 1126, respectively.As highly birefringent material, an active LC layer 1112, 1122 has twodifferent refractive indices, one for each of the two linearpolarization rotation states, whereas the microprism 1116, 1126 has onlyone refractive index in both linear polarization rotation states. Thepassive LC layer 1114, 1124 may be tuned to the same refractive index asthe microprisms 1116, 1126 in one direction, for example 1.49 at 550 nmwavelength for a polymethyl methacrylate (PMMA) polymer layer. Whenvoltage is applied to the transparent electrodes, the interface betweenthe second LC layer 1114, 1124 and the microprism 1116, 1126 has norefractive index difference and is optically transparent to an incomingbeam with the appropriate polarization direction. When the voltage isnot applied, the polarization direction is rotated in the first LC layer1112, 1122 by 90°, and the difference in the indices between the LClayer 1112, 1122 and the microprism 1116, 1126 refracts the beam to afixed steering angle determined by the amount of refractive indexdifference and the prism angle. In the example shown, the shape of theborder between the second LC layer 1114, 1124 and the microprism 1116,1126 in the two light-steering layers 922 and 924 appears to bedifferent, although the light-steering layers 922, 924 may beeffectively identical, for example, with very few differences, such asmanufacturing variances. A first light steering layer may be configuredto deflect light in a first plane, and a second light steering layer maybe configured to deflect light in a second plane substantiallyperpendicular to the first plane. Substantially perpendicular includes,for example, 90±0.01 degrees, 90±0.1 degrees, 90±0.5 degrees, 90±1degree, 90±2 degrees, 90±5 degrees, and so forth. Alternatively, thefirst light steering layer and the second light steering layer may eachbe configured to deflect light in one plane. The two light-steeringlayers 922, 924 may be constructed in the same way with the same shapes,sizes, and materials for each layer, but one layer 924 is rotated, forexample, 90 degrees, 180 degrees, or some other angle, with respect tothe other layer 924 and aligned for a desired optical effect. In someembodiments, one steering layer 922, 924 is arranged horizontally, andthe other steering layer 924, 922 is arranged vertically, e.g., twosubstantially identical layers 922, 924 rotated 90 degrees with respectto each other, to facilitate control of the direction of light from thelight-emitting layer 902 toward any part of the periodic optical layer926. The one or more light-steering layers 922, 924 switch betweendirecting light from one or more light-emitting elements of thelight-emitting layer 902 through one periodic optical feature of theperiodic layer 926 and directing light from one or more light-emittingelements through another periodic optical feature of the periodic layer926. The one or more steering layers 922, 924 may be switched betweendirecting light from one or more light-emitting elements of thelight-emitting layer 902 through three or more different periodicoptical features of the periodic layer 926. Either or both of thelight-steering layers 922, 924 may thus be switchable between directinglight from the light-emitting layer 902 through one periodic feature andthrough any other periodic optical feature of the periodic layer 926.

FIG. 12A and FIG. 12B illustrate examples of repeating optical regionsof periodic optical features of the periodic optical layer 926 inaccordance with some embodiments. One surface of the periodic layer 926includes two or more repeating or periodic features 1202, 1204, 1206,each of which may be configured to have different opticalcharacteristics or properties depending on refractive index, surfaceshape, optical power, and/or surface property. Surface shapes used insome embodiments include, for example, flat facets, continuous curvedsurfaces with different curvature in two directions, and/or diffusingrectangles with optically rough surfaces, among other possible surfaceshapes. In the example of FIG. 12A, the periodic layer 926 is dividedinto multiple optical regions 1208, 1210, 1212, and each optical regionincludes the same set of periodic features 1202, 1204, 1206.Alternatively, the optical regions may include different sets, differentpatterns, and/or different arrangements of periodic features 1202, 1204,1206. The periodic layer 926 may include a repeating pattern of opticalregions 1208, 1210, 1212 within which each of the periodic features1202, 1204, 1206 may be arranged in the same orientation with respect toone another. The optical regions 1208, 1210, 1212 may include differentsurface areas with different patterns of the periodic features 1202,1204, 1206. Alternatively, fewer or additional periodic features may beincluded in one or more repeating optical regions of the periodic layer926. The scale or size of the periodic features 1202, 1204, 1206 and theregions 1208, 1210, 1212 may be chosen in accordance with the overalloptical structure. For example, the optical regions may be smaller thanthe light-converging lenses. Because the effective focal length for eachperiodic feature within an optical region may be selected individually,the geometric magnification ratio may also be selected to achievesmaller source image spots and better resolution. Neighboring lightemitters inside one source array or matrix may be imaged into an arrayor matrix of spots. The use of repeating patterns of periodic featuresover a larger display surface area may lower the cost for manufacturingthe components. For example, a single master tool with fine opticalfeatures may be produced and copied to a larger stamping or molding toolfor large volume production.

FIG. 12A depicts a first side view of an example periodic layer 926,such as shown in FIG. 9 . Three repeating periodic features 1202, 1204,1206, each having different optical properties, are each disposed inthree different optical regions 1208, 1210, 1212, in accordance withsome embodiments. The optical properties of the periodic features maydiffer based on the refractive index of their material, the surfaceshape of the periodic feature, the optical power, and/or a surfaceproperty. By tilting a focused beam appropriately at one or more of thelight-steering layers 922, 924, a particular periodic feature 1202inside one optical region 1208 may be selected. This non-mechanicalswitching technique may be used to select the display beam's propertiesfrom a finite set of options determined by the optical properties of theperiodic features within the optical regions. In the example of FIG.12A, the first periodic feature 1202 may have an optical surface with afirst radius of curvature 1214 and a surface of the feature 1202 may betilted at a first tilting angle 1216 with respect to the optical axis.This surface curvature 1214 may modify the focus distance of incomingbeams. Features with different curvatures may be used to focus thevoxel-forming beams to different distances from the display 200 surface.For example, a first periodic feature may be operative to focus lightfrom a first light-emitting element at first distance from the periodicoptical layer 926, and a second periodic feature may be operative tofocus light from a the first light-emitting element at second distancefrom the periodic optical layer. The second distance is advantageouslydifferent from the first distance. Different periodic optical featuresmay have different tilt angles or different tilt directions thatfacilitate different focus characteristics. Beams steered to the sameperiodic feature 1202 in different optical regions 1208, 1210, 1212 maybe effectively co-axial after or beyond the periodic layer 926 byselective use of the tilt of light. In a similar manner, a secondperiodic feature 1206 may be configured to have a second radius ofcurvature 1218 and a second tilting angle 1220. When the first radius ofcurvature 1214 and the second radius of curvature 1218 are different,the optical properties for the LF display 200 differ. Similarly, whenthe tilting angles 1216, 1220 are different, the optical properties forthe LF display 200 differ. Some of the periodic features 1204, may beconfigured to have a very large (or infinite) radius of curvature 1224R3 that is optically flat and does not affect the focus of thetransmitted beam or light.

FIG. 12B depicts another example of a periodic optical layer, wherein asingle zone 1200 has a pattern of nine periodic features 1202, 1204,1206, 1226, 1228, 1230, 1232. In this example, six of the periodicfeatures 1202, 1206, 1226, 1228, 1230, 1232 are used for focusing andtilting the beams in x and y directions and to different focal depths.These periodic features 1202, 1206, 1226, 1228, 1230, 1232 have smoothand curved surfaces that do not scatter light. Each of the periodicfeatures 1202, 1206, 1226, 1228, 1230, 1232 may have the same opticalproperties, each may have different optical properties, or anycombination of two or more optical properties. The other three periodicfeatures 1204 are identical in this example and may be used to form thevoxels directly on top of the display surface or to create 2D displayimages with higher pixel resolution. These periodic features 1204 mayscatter incident light in order to make pixels visible from all viewingdirections. For example, these periodic features 1204 may have a roughsurface that scatters light.

Periodic features may be arranged in different arrays or patterns on theperiodic layer 926. For example, in some embodiments, the periodicfeatures form a rectangular matrix, wherein the rows and columns arealigned horizontally and vertically in a rectangular grid with no offsetbetween adjacent rows or columns. This pattern may facilitate easierrendering calculations when the generated voxels are also arranged in arectangular matrix or grid. Another example array pattern implemented insome embodiments may have an arrangement with a vertical offset betweenneighboring or adjacent columns, such as in the pattern shown in FIG.12B. This pattern may increase the effective resolution, for example,where only horizontal crossing beams are generated. Alternatively,another example array pattern implemented in some embodiments may havean arrangement with a horizontal offset between neighboring or adjacentrows (not shown). In some embodiments, the pattern of periodic featurearrangement and/or periodic feature properties may differ across thedisplay area. Overlapping display pixel FOV issues may be resolved, forexample, by tilting the beams from the display's edge towards a centralviewing zone by utilizing different periodic features in differentoptical regions across the display area.

In some embodiments, the periodic optical layer 926 may be apolycarbonate sheet with optical shapes made from UV-curable material ina roll-to-roll process. In some embodiments, the periodic layer 926 maybe a layer such as a foil or thin sheet with embossed diffractivestructures. In some embodiments, the periodic layer 926 may be a sheetwith graded index lens features or a holographic grating manufactured byexposing photoresist material to a laser-generated interference pattern.Individual sub-feature sizes and pattern fill-factors may influence theachievable resolution and/or the amount of image contrast, for example,by reducing stray light introduced to the system. When beams aredirected to specific periodic features, aligning the light-emittinglayer 902 with the periodic layer 926 with sufficient accuracy in thehorizontal and vertical directions is advantageous. The light-steeringlayers 922, 924 do not have any characteristics that make accuratealignment critical. The light-steering layers 922, 924 may be used fordisplay calibration by fine-tuning the tilt angles with an appliedvoltage, thereby mitigating at least some of the possible alignmenttolerance issues.

3D LF Display Properties

In some embodiments, an LF display system uses a combination of spatialand temporal multiplexing. When the light-steering component is fastenough to reach an adequate refresh rate, a flicker-free image results.The light-emitting layer 902 and light-steering layers 922, 924 operatetogether to form an image. Accordingly, synchronizing the light-emittinglayer 902 and light-steering layers 922, 924 may be advantageous. Thedisplay 200 generates signals to control illumination of an addressablearray of light-emitting elements of the light-emitting layer 902 and tocontrol steering properties of at least one of the light-steering layers922, 924 in a time synchronized manner in some embodiments. For example,the light-steering layer may select the focal plane where the projectedbeams are focused. Because the periodic layer 926 has fixed periodicoptical features, this synchronization may be implemented in someembodiments by utilizing a look-up table that connects thelight-steering layer control parameters to the individual beam focaldepths and angles of the periodic features. Such a table may simplifythe controls for image rendering, because the parameters arepredetermined for each display. In some embodiments, light-emittingcomponents may be activated individually or in groups that, for example,form a voxel at a specific point in space. In some embodiments, a groupof emitters may form one half of a series of neighboring voxels for anindividual eye of a single viewer and a different group of emitters mayform the other half of the voxels for the other eye. The controlparameters may optionally be calibrated for individual displays byperforming measurements that connect, for example, a single emitteractivation and a beam steering voltage to a specific measured beam focusdepth and angular direction values. Faster refresh rates oflight-emitting components such as μLEDs may be used advantageously. Forexample, the light sources may be activated several times within therefresh rate of the beam steering component. In some embodiments, eyetracking may be used to lower the requirements for the refresh rate orupdate speed. For example, images may be rendered to a subset ofspecified eye-box regions instead of to the whole display FOV.

FIG. 13 illustrates the spatial multiplexing function of an LF display200, in accordance with some embodiments. In the example, an array ormatrix of light emitters 1302, also referred to as an addressable arrayof light-emitting elements, behind each focusing lens 1304 generates agroup of beams that are focused close to the periodic features of theperiodic layer 926. The features alter the focus distance andpropagation angle of each beam, and the individual sources are imaged,for example, at one or more focal points 1306 on the display 200, at oneor more focal points 1308, 1310 in front of the display 200, and/or atone or more focal points 1312, 1314 behind the display 200. Theresulting source images are larger than the sources, and the opticalmagnification ratio is determined, for example, by the combination offocusing lens 1304 and periodic feature focal lengths. The pitch orangle of the focusing element may be configured to be the same as theperiodic feature pitch or angle in order to address individual periodicfeatures of the periodic layer 926 without use of light-steering layers.Light sources or light-emitting elements 1302 may be arranged intoclusters or groups that may have sub-groups of components that areimaged to one periodic feature at a time. With proper arrangement, theneighboring sources or sub-groups 1302 create beams that exit thestructure 926 in the same direction but have different focus distances.An example of this function is shown in FIG. 13 with the beams that havedifferent focal points 1306, 1308, 1312. Light sources 1302 or sourcesub-groups at the edge of the display may also create beams that strikeneighboring periodic layer features, in which case the beams exit thedisplay 200 at steeper angles, thereby increasing the projected imageFOV. Examples of this effect are illustrated by the beams having focalpoints 1314, 1310 projected at associated view angles 1316, 1318,respectively.

In some embodiments, a light field display 1300 may operate without anylight-steering layer, such as presented in FIG. 13 . In suchembodiments, only spatial multiplexing is used to generate the multiplecrossing beams and focal layers necessary for a 3D image. Accordingly, atrade-off may be found between the number of pixels used for each focallayer and each view direction, because individual emitters may eachprovide only single beams that propagate in a single direction and havea single focus point. For example, the projected image of the lightsource positioned in the middle of the source matrix may have one focuspoint 1306, and the projected image of the light source next to acentral light source may have another focus point 1308. Light-steeringlayers may increase picture quality by adding temporal multiplexing tothe system. Light-steering layers may provide the ability to change thedistance at which image layers are projected without compromisingspatial resolution. This effect may help provide higher resolutionimages or lower cost structures that have fewer light-emittingcomponents 1302.

In some embodiments, the optical system of a display 1400 may usecrossing beams to form voxels, such as shown in FIG. 14 . The voxels maybe formed at different distances both in front of and behind the displayas well as on the display surface. In the example of FIG. 14 , anexample voxel 1402 is depicted. This voxel 1402 is created in front ofthe display 1400 at a specific focal distance using three beamsoriginating from three different sources 1302. Two of these beams(bottom and middle) are created without beam steering, but the thirdbeam (top) is directed and focused at the voxel location by thelight-steering layers 922, 924 and temporal multiplexing. Another voxel1404 is displayed behind the display 1400 by crossing the virtualextensions of two beam sections emitted from two different sources.Single beams with specific focus distances are used to generate correcteye retinal focus cues, whereas multiple beams crossing at the voxelpositions are used to cover the larger FOV of the viewer eye pair. Thisconfiguration may provide the visual system with the correct eyeconvergence. In this manner, the generation of small light emissionangles for single eye retinal focus cues and larger emission angles foreye convergence, for example, to create a stereoscopic effect, areseparated from each other in the optical structure. The arrangement mayprovide the ability to control the two angular domains separately withthe display's optical characteristics or properties. Focal surfacedistances may be coded and stored in the optical hardware as the opticalpowers of the periodic features, which may fix the voxel depthco-ordinates at discrete positions. The rendering task may be relativelysimplified because the single eye retinal focus cues are created withsingle emitter beams. For example, one voxel may be formed using onlytwo beams from two emitters. Some embodiments may use more beams tocreate each voxel, for example, when wider eye-boxes or viewing zonesare desired.

One factor that may be considered in the design of 3D LF displays isthat optical materials refract light with different wavelengths atdifferent angles (color dispersion). If three colored pixels, such asred, green, and blue sub-pixels, are used, the different colored beamsare tilted and focused in somewhat different directions and at somewhatdifferent distances from the refractive features. In some embodiments,color dispersion may be compensated for in the display by using a hybridlayer where, for example, diffractive features are used for colorcorrection. Because colored sub-pixels may be spatially separated on thelight-emitting layer, some small angular differences between the coloredbeam projection angles may result. If the projected images of the sourcecomponents are kept small enough on the focal surface layers, thethree-colored pixels will be imaged next to each other and combined intofull-color voxels by the eye in a similar manner analogous to how 2Dscreens render images where the colored sub-pixels are spatiallyseparated. The colored sub-pixel images of the 3D display are highlydirectional, and ensuring that all three differently colored beams enterthe eye through the pupil is advantageous. For example, implementing thelight concentrator and color mixing structures described herein may beadvantageous.

Diffraction may also affect the achievable resolution, for example, whenthe light emitter and focusing lens aperture sizes are very small. Thedepth range achievable with the light field display and real LFrendering scheme may be affected by the quality of beam collimation orconvergence coming from each sub-pixel. Parameters that may determinecollimation or convergence quality include the sizes of thelight-emitting sources, the size of the periodic layer zone aperture,and the effective focal length. A continuous light emitter matrix on thelight-emitting layer may facilitate very wide FOVs. An increase in thedifficulty of addressing all periodic layer features accurately when thebeams are projected to larger angles may, however, limit the achievableFOV. Some fine-tuning of beam positions at the light-steering layers tolarger angles may mitigate the problem of reduced FOV. In someembodiments, other beam steering components such as electrowettingmicroprisms may be implemented, for example, to better control the beamsteering angles.

3D LF Display Rendering Schemes

Several different kinds of rendering schemes may be used together withthe display structures and optical methods described herein. Dependingon the selected rendering scheme, a display device may be a 3D lightfield display with multiple views and focal surfaces or a regular 2Ddisplay. 2D functionality may be supported by making some of theperiodic features optically diffuse, whereby the single beams arevisible in a large FOV.

In some embodiments, a 3D LF rendering scheme generates several focalpoints or focal surfaces in front of or behind the physical displaysurface in addition to the multiple viewing directions. Generating atleast two projected beams for each 3D object point or voxel isadvantageous. Reasons for using at least two beams may include (i) thata single emitter inside the display should have an FOV that makes itvisible to only one eye at any given time, and (ii) that the createdvoxel should have an FOV that covers both eyes simultaneously to createthe stereoscopic view. The voxel FOV may be generated as a sum ofindividual beam FOVs when more than one beam is used at the same time.For all voxels that are displayed between the display and the observer,crossing the convergence beams in front of the display at the correctvoxel distance may be advantageous. For the voxels positioned at afurther distance from the observer than the display, crossing a beampair virtually behind the display may be advantageous. The crossing ofat least two beams generates a focal point or surface that is not onlyon the display surface. Focusing the separate beams at the same pointwhere they cross may be advantageous. More natural retinal focus cuesmay be created by generating a single beam focused at periodic featuresin the periodic layer 926.

Rendering a truly continuous range of depths with a 3D LF display mayinvolve heavy computation. In some embodiments, the 3D data may bereduced to a fixed number of discrete depth layers to reducecomputational requirements. In some embodiments, discrete depth layersmay be arranged close enough to each other to provide the observer'svisual system with a continuous 3D depth experience. Covering the visualrange from 50 cm to infinity may take about 27 different depth layers,based on the estimated human visual system average depth resolution. Insome embodiments, the methods and optical hardware described hereinfacilitate creation of multiple focal surfaces that may be displayed atthe same time, or inside the visual system persistence-of-vision POVtimeframe due to spatially separated features that are used for thedepth layer selection. In some embodiments, observer positions may beactively detected by the LF display and voxels may be rendered in onlythose directions where the observers are located. In some embodiments,active observer eye tracking is used to detect observer positions, forexample, using near-infrared (NIR) light with cameras around or in thedisplay structure.

One trade-off associated with the rendering scheme may be found betweenspatial/angular and depth resolutions. Given a limited number of pixelsand component switching speeds, emphasizing high spatial/angularresolution may result in fewer focal planes or lower depth resolution.Conversely, having more focal planes for better depth resolution mayresult in a more pixelated image or low spatial/angular resolution. Thesame tradeoff may apply to data processing at the system level, becausemore focal planes may involve more calculations and higher data transferspeeds. In the human visual system, depth resolution decreaseslogarithmically with distance, which may facilitate reduction of depthinformation when objects are farther away. The eyes can resolve onlylarger details as the image plane goes farther away, which mayfacilitate the reduction of resolution at far distances. In someembodiments, rendering schemes are optimized by producing differentvoxel resolutions at different distances from the viewer to lower theprocessing requirements for image rendering. The tradeoffs connected tothe rendering scheme may also be addressed based on the presented imagecontent, enabling, for example, higher resolution or image brightness.

In some embodiments, three differently colored light emitters may beimplemented on the light-emitting layer 902 in order to create afull-color picture. The color rendering scheme may involve systemsand/or methods to adapt to the different colors that are refracted atsomewhat different angular directions at the periodic layer 926. Inaddition to a special color rendering scheme, some of this dispersionmay be removed with hardware, for example, by integrating diffractivestructures for color correction, which may compensate for differentfocus distances of the refractive periodic features. An example colorrendering scheme, in accordance with some embodiments, uses whiteillumination by combining the output of three differently coloredcomponents with an optical light mixing structure as described herein,and the beam color may be selected with the light-emitting layercontrols.

Implementation Examples

FIG. 15 depicts a curved 3D light field display 1502 device viewed froma particular distance by a viewer 1504, in accordance with someembodiments. In this example, a 14 inch desktop 3D LF display is viewedfrom a distance 1506 of 500 mm. The display screen is curved with a 500mm radius such that single display LF pixel emission patterns overlap atthe viewer 1504 position. Single LF pixels emit light to approximately42° FOV in this example. An approximately 380 mm wide viewing window isformed around the viewer eyes to provide adequate head and eye movementsfor a single user in this example.

FIG. 16A is a representation of two light concentrators 1602, 1604 of alight-emitting layer 902, in accordance with some embodiments. A μLEDcluster 1606 is implemented as four 2 μm×2 μm μLEDs positioned in arectangular pattern, such as shown in the side view 1608 (looking intothe concentrator from the left side of the drawing), where pitch betweenthe centers of the μLEDs is 3 μm. Each cluster 1606 has one red R, oneblue B, and two green G μLEDs as shown in the side view 1608. Sides ofonly the R and G μLEDs from the right side of the cluster 1606 of theside view 1608 are shown within the concentrators 1602, 1604 in FIG.16A. The μLED clusters 1606 may be overmolded into a structure includinga light concentrator 1602, 1604 and color mixer 1610, 1612,respectively, which structure concentrates the total emission pattern ina 30° cone 1614, 1616, respectively. The exit aperture size of theconcentrators 1602, 1604 is 12 μm×12 μm in this example. The front facetof the concentrator is curved in order to reach the Numerical Aperture(NA) that facilitates high energy efficiency in the optical path of theentire display.

FIG. 16B is a representation of a light source matrix 1600 of alight-emitting layer 902 in accordance with some embodiments. In theexample, light-emitting elements in the form of light source clusterswith integrated concentrators 1620 are arranged into a 21×21 matrix andbonded to a substrate 1622 thereby forming a sub-assembly. The substratehas electrical contacts 1624 that may individually activate each μLEDlight source. The electrical contacts 1624 and light clusters 1620 forman addressable array of light-emitting elements. The display generatessignals to control illumination of the addressable array oflight-emitting elements of the light-emitting layer 902 and to controlsteering properties of at least one of the light-steering layers 922,924 in a time synchronized manner. The pitch between adjacent full-colorintegrated sources is 14 μm, making the total width of the matrix 292μm. The concentrators at the edge of the matrix have tilted front facetsthat tilt the emission patterns by a 10° tilt angle 1618 towards theoptical axis 1604 of the array as shown in FIG. 16A and FIG. 16B. Insome embodiments, front facets vary in angle through the matrix in sucha way that the emission pattern centerlines meet at an 800 μm distancein front of the matrix in this example. This distance may provide veryhigh optical efficiency and low stray light performance by reducingwasted light to the outside of the light collecting lens aperture thatfollows. In the example shown in FIG. 16B, the integrated sources aregrouped into 7×7 source clusters 1622 that are 96 μm wide.

FIG. 17 is a representation of the optical design of a display, inaccordance with some embodiments. FIG. 17 presents an example designwith measurements (in μm) of the display's optical structure, which isapproximately 4 mm thick. In the example, light emitted from the sourcematrix 1600 of the light-emitting layer 902 is collected and focusedwith two plano-convex microlens arrays 1702, 1704 of the converging lenslayer 920, which arrays 1702, 1704, may be manufactured by hot embossingPMMA material. The lens aperture sizes are 600 μm×600 μm in thisexample. The first lens 1702 has a focal length of 800 μm and collectsthe emitted light in this example. The second lens 1704 has a focallength of 1670 μm and focuses the light through two light-steeringlayers 922, 924 to the periodic features 1706, 1708, 1710 of theperiodic layer 926 in this example. The periodic features 928, 930, 932have at least one different optical property from one another, forexample, refractive index, light scattering, and a surface property,such as shape or radius of curvature. A 200 μm thick linear polarizersheet or foil 918 is laminated to the collector microlens 1702 in thisexample. The second lens 1704 is laminated to a stack that contains two400 μm thick light-steering layers or components 922, 924 that operatein conjunction with a combination of liquid crystal materials andpolymer microprisms as described herein. The light-steering layers 922,924 may tilt the focused beams by 8.7° in the counterclockwise directionabove the optical axis and by 12.5° clockwise in the horizontal plane inthis example. These tilt angles may facilitate the steering of theemitter cluster images from one optical region 1712 of the periodiclayer 926 to the next optical region 1714 of the periodic layer 926given the 800 μm distance between the layer stack and the periodic layer926 in this example.

In the example shown in FIG. 17 , the periodic layer 926 is integratedto a 1.2 mm thick display protective window 1718, which is made frominjection molded PMMA material. The outer surface 1720 of the protectivewindow 1718 may be the outer surface of the LF display 1700 and thus maybe touched by the viewer. The width of each repeating optical region1712, 1714, 1716 is 600 μm and each optical region 1712, 1714, 1716contains three 200 μm periodic features 1706, 1708, 1710, each withdifferent optical properties in this example. Each of the opticalregions 1712, 1714, 1716 shown in this example have a negative opticalpower, thus the incoming focused beams diverge. In this example, thefirst periodic feature 1706 has a focal length of −240 μm and focusesthe beams at ˜100 mm distance from the display surface 1720 toward theviewer. In this example, the second periodic feature 1708 has a focallength of −340 μm and focuses the beams on the front surface 1720 of theprotective window 1718. In this example, the third periodic feature 1710has a focal length of −230 μm and is to form voxels behind the displayat ˜200 mm distance by the virtual extensions of the beams. The firstand third periodic features 1706, 1710 have optical apertures that areoffset from the optical axis 1722 facilitating 5.6° beam tilt. This beamtilting may be used to compensate for the tilt coming from differentlight source cluster positions off the optical axis 1722. In thisexample, all three optical regions are able to project beams in the samecentral direction when the beam tilting elements are not activated, asshown in the example ray trace diagram in FIG. 18 . The display 200 isconfigured to generate signals that control illumination of theaddressable array of light-emitting elements and signals that controlsteering properties of the light-steering layers 922, 924. The signalsare synchronized. The signals that control steering properties of thelight-steering layers 922, 924 may be, for example, beam steeringvoltages applied to the light-steering layers 922, 924. The signals maybe generated, for example, by a processor 118 executing instructionsstored in memory. A periodic feature 928, 930, 932, 1706, 1708, 1710 isselected based on depth information for a three-dimensional imagerendered on the display 200. Light emitted by a light-emitting elementis steered toward one of the periodic optical features based on depthinformation of the image being displayed. Light is directed through thesteering layers 922, 924 to the selected periodic feature to producevoxels that focus at various distances 934, 938, 942 from a surface ofthe display 200 to produce a three-dimensional image. Although onlythree distances are specifically shown, any number of distances may bedisplayed within a range of distances in front of and behind thedisplay. An example projector cell 1724 in the display 1700 includes aset of corresponding components, for example, a plurality oflight-emitting elements 1600, converging lenses of the lens arrays 1702,1704, a section of the light-steering layers 922, 924, and an opticalregion 1716 of the periodic layer 926.

FIG. 18 is an example of an optical ray trace diagram depicting lightfrom three source clusters 1802 traversing focusing lenses 1702, 1704,light-steering layers 922, 924, and a periodic layer 926 with aprotective window 1720. In the example, the optical magnification of thelight collecting lenses 1702 and focusing lenses 1704 is ˜2.1, thus theimage of one 7×7 source cluster 1802 is ˜200 μm wide. This size imagefits inside the area of a periodic feature 1804, 1806, 1808, thusfacilitating the projection of such matrix images from all periodicfeatures 1804, 1806, 1808 to different focal planes determined by theoptical powers of the periodic features 1804, 1806, 1808. The centralperiodic feature 1806 focuses this matrix image to the front surface1720 of the protective window 1718, which surface 1720 is the exitsurface of the entire display structure 1800. Total magnification ofthis optical feature structure is ˜6.25 in this example, thus a singlefull-color emitter is imaged to ˜85 μm full-color pixel in this example.A 14-inch display typically has an array of 3840×2160 pixel clusters,resulting in a 4K display.

Also shown in FIG. 18 , a single source image beam is projected out ofthe display 1800 through the central periodic feature 1806 and creates˜70 mm diameter blurred spot at the designated 500 mm viewing distance.In some situations, the eye pupils function as the limiting aperture.Because the spot is so wide, the same light source is visible to botheyes that have approximately 64 mm pupil separation. Thus, the voxelcreated with central periodic feature 1806 is positioned on the displaysurface 1720 and should be visible to both eyes at the same time. Thesingle source beams projected through the first periodic feature 1804and the third periodic feature 1808 create ˜55 mm wide spots at the 500mm viewing distance. The smaller spots result from the beam convergencecoming through aspects of the periodic features' 1804, 1808 withdifferent focal lengths, resulting in the system imaging the lightsources with less blur to the viewer position or location. The smallerspot is not visible to both eyes at the same time, and two beamscrossing outside the display surface 1720 may form voxels withoutcontradicting retinal focus cues. In some embodiments, thelight-steering layers 922, 924 facilitate beam crossing only in thehorizontal direction, but because the emitter matrices 1802 andmicrolens arrays 1702, 1704 are two-dimensional, two dimensional beamsare generated. Voxel formation may be provided by virtue of the fixedpositioning of the display 1800 with respect to horizontally spacedeyes. Voxel resolution may be determined by the size of the eye pupilbecause this size may be the limiting optical aperture.

A method of displaying a three-dimensional image is shown in theflowchart of FIG. 19 . The flowchart may be performed, for example, bysoftware executed by one or more processors of the display 200. Themethod may include additional or few processes than shown and/ordescribed and may be performed in a different order. Computer-readablecode executable by one or more processors to perform the method may bestored in a computer-readable medium, such as a non-transitorycomputer-readable medium. An image comprising a plurality of voxels isdisplayed by displaying or projecting a plurality of voxels at aplurality of voxel positions. One or more of the periodic features 928,930, 932, 1706, 1708, 1710 of the periodic optical layer 926 is selected1902 based on depth information of a pixel of a three-dimensional imagerendered by the display 200 and one or more optical properties of theperiodic feature(s) 928, 930, 932, 1706, 1708, 1710. Light emitted by alight-emitting element is steered toward one of the periodic opticalfeatures based on depth information of the image being displayed. Thedisplay 200 selectively emits light from pixels or light-emittingelements of an addressable array of light-emitting elements 1600 byactivating 1904 pixels or light-emitting elements associated with datafor the 3D image being rendered. Light emitted from the pixels orlight-emitting element of the addressable array of light-emittingelements 1600 of the light-emitting layer 902 is directed toward one ormore of the selected periodic features 928, 930, 932, 1706, 1708, 1710to focus light at various distances from a surface 1720 of the display200 based on the data for the 3D image being rendered or displayed.Light may be focused at one or more distances in front of, at thesurface 1720 of, and at one or more distances behind the surface of thedisplay 200. The emitted light is directed by operating 1906 at leastone light-steering layer 922, 924 to direct the emitted light toward oneor more selected periodic features 928, 930, 932, 1706, 1708, 1710. Theemitted light may be directed in a time-synchronized manner toward theselected periodic features 928, 930, 932, 1706, 1708, 1710.Alternatively, the emitted light may be directed in a time-multiplexedmanner toward the selected periodic features 928, 930, 932, 1706, 1708,1710. Applying a voltage to at least one of the light-steering layers922, 924 directs light from the emitters toward the periodic layer 926.A first section of the light-steering layer 922, 924 may be operated toselectively direct light from a first light-emitting element toward afirst periodic optical feature of the periodic optical layer 926, andthe first periodic optical feature focuses the light onto a first voxelposition. A second section of the light-steering layer 922, 924 may beoperated to selectively direct light from a second light-emittingelement toward a second periodic optical feature of the periodic opticallayer 926, and the second periodic optical feature focuses the lightonto the first voxel position. A third section of the light-steeringlayer 922, 924 may be operated to selectively direct light from a thirdlight-emitting element toward a third periodic optical feature of theperiodic optical layer 926, and the third periodic optical featurefocuses the light onto a second voxel position. The first voxel positionmay have a first depth, and the second voxel position may have a seconddepth different from the first depth. The light-steering layer(s) 922,924 may be controlled on a pixel basis. Signals to selectively emitlight from the pixels may be generated, for example, individually or byany combination of the display 200, a processor associated with thedisplay, and software storing data for creating the signals. The lightpassing through the selected periodic features 928, 930, 932, 1706,1708, 1710 may advantageously produce crossing beams that are used toform voxels, for example, at distances in front of the display 200, atthe surface 1720 of the display 200, and at distances behind the display200. The light exiting the outer surface 1720 of the display 200 may befocused into a set of beams that forms an image in different viewingdirections.

Some of the described methods and optical structures are more suitablefor large screen sizes because diffraction effects limit the achievablefocused beam spot size in smaller displays that call for very smallprojector cell aperture sizes. Generation of correct retinal focus cuesmay be lost when diffraction blurs the source image too much. Thepresented optical features scale together with the display size. Someembodiments may be implemented using large scale manufacturing methods,such as roll-to-roll nanoimprinting.

The non-mechanical light-steering layers used in some embodiments may beproduced with materials, such as liquid crystal (LC), and processes thatare known in the display industry. Some embodiments may use LCtechnology that employs linearly polarized light, which lowers opticalefficiency of the system and increases power consumption.

A display may operate to produce voxels at multiple focal planes. Thevoxels may be produced by generating light beams that focus at one ormore different distances from the display surface. The display mayinclude a light-emitting layer including a plurality of cells, alsoknown as light-emitting elements, comprised of light sources and lightcollimating or converging optical structures; a periodic optical layercomprising a repeating pattern of optical regions, wherein each opticalregion comprises a plurality of spatially arranged periodic featureswith differing optical refractive and scattering properties; and atleast one light-steering layer. The display generates signals to controlthe illumination of the light-emitting elements and the steeringproperties of the at least one light-steering layer in a timesynchronized manner. The steering properties of the one or morelight-steering layers may be optionally controllable at a pixel level. Asignal generated to control the steering properties of a steering layermay optionally be generated to cause the steering layer to steer a beamof light generated by an illuminated light-emitting element to aselected periodic feature of the periodic layer, wherein the periodicfeature is selected based on depth information of 3D content beingrendered by the display. The light-emitting layer may optionallycomprise a cluster of light emitters comprising light concentratorshaving a first geometry and a second geometry, where the lightconcentrators having the second geometry are disposed along one or moreedges of the cluster. The optical properties of the spatially arrangedperiodic features may optionally differ based on the refractive index ofthe material, the surface shape of the periodic feature, and/or asurface property. The spatially arranged periodic features mayoptionally be offset vertically and/or horizontally to increase theeffective resolution of the display.

A display comprises an addressable array of light-emitting elements; aperiodic optical layer comprising a plurality of repeating regions,wherein two or more of the repeating regions each comprise a firstperiodic feature having a first optical property and a second periodicfeature having a second optical property; at least one light-steeringlayer disposed between the addressable array of light-emitting elementsand the periodic optical layer, wherein the light-steering layerprovides selective control over a direction of light reaching theperiodic optical layer from the addressable array of light-emittingelements, such that light is focused at various distances from a surfaceof the display, A beam of light may be steered toward one of the firstperiodic feature and the second periodic feature based on depthinformation of a three-dimensional image rendered by the display. Asignal generated to control steering properties of the at least onesteering layer may cause the steering layer to steer a beam of lightgenerated by the addressable array of light-emitting elements to aselected periodic feature of the periodic optical layer. The selectedperiodic feature may be selected based on depth information of athree-dimensional image rendered by the display. The first opticalproperty may differ from the second optical property by at least arefractive index, surface shape, optical power, and/or surface property.The display may be configured to generate signals that controlillumination of the addressable array of light-emitting elements andsignals that control steering properties of the at least onelight-steering layer in a time synchronized manner to produce voxelsthat focus at various distances from the surface of the display. Thefirst periodic feature may focus light at a first distance from asurface of the display and the second periodic feature may focus lightat a second distance from the surface of the display. A third periodicfeature may focus light in a first direction, and a fourth periodicfeature may focus light in a second direction. A first light-steeringlayer may be arranged substantially perpendicularly to a secondlight-steering layer. The plurality of repeating regions may be offsetvertically or horizontally from each other to increase effectiveresolution of the display. The addressable array of light-emittingelements may comprise a plurality of light emitters constructed with aplurality of light concentrators having tilted front facets near an edgeof the array.

A method comprises selecting a periodic feature from a plurality ofperiodic features arranged in repeating regions of a periodic opticallayer. The periodic feature is selected based on depth information of avoxel of a three-dimensional image rendered by a display and at leastone optical property of the periodic feature. The three-dimensionalimage is rendered by the display by selectively emitting light from anaddressable array of light-emitting elements and by operating at leastone light-steering layer in a time synchronized manner to direct theemitted light toward one or more selected periodic features to focuslight at various distances from a surface of the display. Crossing beamsmay be used to form the voxels at distances in front of the display anddistances behind the display. A first periodic feature of the pluralityof periodic features may have a first optical property, and a secondperiodic feature of the plurality of periodic features may have a secondoptical property that is different from the first optical property.Operating may comprise applying a voltage to the at least onelight-steering layer. Light may be focused as a set of beams that forman image in different viewing directions. Light may be steered towardone of the first periodic feature and the second periodic feature basedon depth information of a three-dimensional image rendered by thedisplay. A signal generated to control steering properties of the atleast one steering layer may cause the steering layer to steer lightgenerated by the addressable array of light-emitting elements to aselected periodic feature of the periodic optical layer. The selectedperiodic feature may be selected based on depth information of athree-dimensional image rendered by the display.

Systems and methods are described for producing voxels at multiple focalplanes. The voxels are produced by generating light beams that focus atvarious distances from the display surface. In some embodiments, adisplay includes a light-emitting layer, a periodic optical layer, andone or more light-steering layer(s). The light-emitting layer includes aplurality of cells, each cell including at least one light-emittingelement. The periodic layer may include a repeating pattern of regions,and each region may comprise a plurality of spatially arranged periodicfeatures with differing optical refractive and/or scattering properties.The display controls the illumination of the light-emitting elements andthe steering properties of the light-steering layer(s) in a timesynchronized manner.

Note that various hardware elements of one or more of the describedembodiments are referred to as “modules” that carry out (e.g., perform,execute, and the like) various functions that are described herein inconnection with the respective modules. As used herein, a moduleincludes hardware (e.g., one or more processors, one or moremicroprocessors, one or more microcontrollers, one or more microchips,one or more application-specific integrated circuits (ASICs), one ormore field programmable gate arrays (FPGAs), one or more memory devices)deemed suitable by those of skill in the relevant art for a givenimplementation. Each described module may also include instructionsexecutable for carrying out the one or more functions described as beingcarried out by the respective module, and it is noted that thoseinstructions could take the form of or include hardware (e.g.,hardwired) instructions, firmware instructions, software instructions,and/or the like, and may be stored in any suitable non-transitorycomputer-readable medium or media, such as commonly referred to as RAM,ROM, and so forth.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable storage media include, butare not limited to, a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs). A processor in association with software may be used toimplement a radio frequency transceiver for use in a WTRU, UE, terminal,base station, RNC, or any host computer.

What is claimed is:
 1. An apparatus for displaying an image by anoptical system, comprising: a light-emitting layer comprising anaddressable array of light-emitting elements including a firstlight-emitting element; a periodic optical layer overlaying thelight-emitting layer, the periodic optical layer comprising at least afirst periodic optical feature having a first optical power and a secondperiodic optical feature having a different optical power; and a firstcontrollable light-steering layer between the light-emitting layer andthe periodic optical layer, wherein the first controllablelight-steering layer is switchable between directing light from thefirst light-emitting element through the first periodic optical featureand directing light from the first light-emitting element through thesecond periodic optical feature, wherein the directed light through thefirst periodic optical feature and through the second periodic opticalfeature is focused on a position of a voxel of the displayed image. 2.The apparatus of claim 1, wherein the first periodic optical feature andthe second periodic optical feature are included in a first opticalregion, and wherein the periodic optical layer comprises a repeatingpattern of optical regions arranged similarly to the first opticalregion.
 3. The apparatus of claim 1, further comprising a converginglens layer between the light-emitting layer and the periodic opticallayer.
 4. The apparatus of claim 3, wherein the converging lens layercomprises a two-dimensional array of converging lenses, and wherein eachconverging lens is associated with at least one of the light-emittingelements in a projector cell.
 5. The apparatus of claim 4, wherein eachprojector cell includes a corresponding optical region of the periodicoptical layer.
 6. The apparatus of claim 4, wherein different sectionsof the first controllable light-steering layer are associated withdifferent projector cells and are separately controllable.
 7. Theapparatus of claim 1, wherein the first periodic optical feature isoperative to focus light from at least the first light-emitting elementat a first distance from the periodic optical layer, and the secondperiodic optical feature is operative to focus light from at least thefirst light-emitting element at a second distance from the periodicoptical layer, wherein the second distance is different from the firstdistance.
 8. The apparatus of claim 1, wherein the first controllablelight-steering layer comprises at least one liquid crystallight-steering layer.
 9. The apparatus of claim 1, wherein thelight-emitting layer further comprises a second light-emitting element;wherein the periodic optical layer further comprises a third periodicoptical feature having a first tilt direction and a fourth periodicoptical feature having a second tilt direction different from the firsttilt direction; and wherein the first controllable light-steering layeris switchable between directing light from the second light-emittingelement through the third periodic optical feature and directing lightfrom the second light-emitting element through the fourth periodicoptical feature.
 10. The apparatus of claim 1, further comprising asecond controllable light-steering layer between the light-emittinglayer and the periodic optical layer.
 11. The apparatus of claim 10,wherein the first controllable light-steering layer is configured todeflect light in a first plane, and the second controllablelight-steering layer is configured to deflect light in a second planesubstantially perpendicular to the first plane.
 12. The apparatus ofclaim 10, wherein the first controllable light-steering layer and thesecond controllable light-steering layer are each configured to deflectlight in a first plane.
 13. The apparatus of claim 1, wherein at leastone of the first periodic optical feature and the second periodicoptical feature comprises a rough surface that scatters light.
 14. Amethod for displaying an image by an optical system, comprising:displaying an image comprising a plurality of voxels including a firstvoxel at a first voxel position by: selectively emitting a first lightby a first light-emitting element of a light-emitting layer, comprisinga plurality of light-emitting elements; operating a first section of acontrollable light-steering layer to selectively direct light toward afirst periodic optical feature of a periodic optical layer, comprising aplurality of periodic optical features, wherein the first periodicoptical feature has a first optical power and focuses the first lightonto the first voxel position; selectively emitting a second light by asecond light-emitting element of the light-emitting layer; and operatingat least a second section of the controllable light-steering layer toselectively direct the second light toward a second periodic opticalfeature of the periodic optical layer, wherein the second periodicoptical feature has a different optical power and focuses the secondlight onto the first voxel position.
 15. The method of claim 14, furthercomprising, for at least a second voxel in the image having a secondvoxel position: selectively emitting third light by at least a thirdlight-emitting element of the light-emitting layer; and operating atleast a third section of the controllable light-steering layer toselectively direct light toward a third periodic optical feature of theperiodic optical layer, wherein the third periodic optical featurefocuses the third light onto the second voxel position.
 16. The methodof claim 15, wherein the first voxel position has a first depth and thesecond voxel position has a second depth different from the first depth.17. The method of claim 14, wherein light emitted by one of theplurality of light-emitting elements is steered toward one of theplurality of periodic optical features based on depth information of theimage.
 18. The method of claim 14, wherein at least one of the pluralityof periodic optical features comprises a rough surface that scatterslight.